is this the reason __at the meeting for his carelessness in his work?

问题描述:

is this the reason __at the meeting for his carelessness in his work?
A he explained
B what he explained
c how he explained
d why he explained
为什么选A 怎么看出reason在句中的当宾语啊?

A
是that he explained 的省略
考虑正常语序:
he explained the reason at the meeting